Ornamental lamp



FIG. 1 is a perspective view of an ornamental lamp showing my new design;

FIG. 2 is a front elevation view thereof; the rear elevation view, the left side elevation view and the right side elevation views are identical to that shown;

FIG. 3 is a top plan view thereof; and,

FIG. 4 is a bottom plan view thereof. 

The ornamental design for an ornamental lamp, as shown and described. 